[ https://issues.apache.org/jira/browse/PIG-1510?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Daniel Dai updated PIG-1510:
----------------------------
Status: Resolved (was: Patch Available)
Hadoop Flags: [Reviewed]
Resolution: Fixed
Patch committed to trunk. Thanks Swati for contributing!
> Add `deepCopy` for LogicalExpressions
> -------------------------------------
>
> Key: PIG-1510
> URL: https://issues.apache.org/jira/browse/PIG-1510
> Project: Pig
> Issue Type: New Feature
> Components: data
> Affects Versions: 0.8.0
> Reporter: Swati Jain
> Assignee: Swati Jain
> Fix For: 0.8.0
>
> Attachments: deepCopy.patch, deepCopy.patch
>
>
> It would be useful to have a way to `deepCopy` an expression. `deepCopy` will create
a new object so that changes made to one object will not reflect in the copy. There are 2
reasons why we don't override clone.
> * It may be better to use `deepCopy` since the copy semantics are explicit (since deepCopy
may be expensive).
> * A second important reason for defining `deepCopy` as a separate routine is that it
can be passed a plan as an argument which will be updated as the expression is copied (through
plan.add and plan.connect).
> The usage would look like the following:
> {noformat}
> LogicalExpressionPlan logicalPlan = new LogicalExpressionPlan();
> LogicalExpression copyExpression = origExpression.deepCopy( logicalPlan );
> {noformat}
> An immediate motivation for this would be for constructing the expressions that constitute
the CNF form of an expression.
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